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Notes on Thescelosaurus, a Conservative Ornithopod Dinosaur from the Upper Cretaceous of North America, with Comments on Ornithopod Classification

Peter M. Galton
Journal of Paleontology
Vol. 48, No. 5 (Sep., 1974), pp. 1048-1067
Stable URL: http://www.jstor.org/stable/1303302
Page Count: 20
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Notes on Thescelosaurus, a Conservative Ornithopod Dinosaur from the Upper Cretaceous of North America, with Comments on Ornithopod Classification
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Abstract

The skull of Thescelosaurus had broad frontals and there is a well-defined area of attachment for a cheek on the mandible. Wear surfaces were formed on some premaxillary teeth by contact with the predentary. The cheek teeth have either single or double wear surfaces. The large first sacral rib of lower ornithopods was important in keying together the pubis and the ilium and for backing the slender pubic peduncle of the ilium. Thescelosaurus edmontonensis Sternberg is probably a junior synonym of T. neglectus Gilmore. Thescelosaurus retains many features, including premaxillary teeth, which are primitive for ornithopods (and ornithischians) as a group but this genus was probably graviportal and possibly even more quadrupedal than most other ornithopods. The family Hypsilophondontidae is restricted to cursorial forms and Thescelosaurus is transferred to the family Iguanodontidae, which includes all the generalized graviportal ornithopods lacking the cranial specializations of hadrosaurs and pachycephalosaurs. The family Iguanodontidae probably represents a grade of organization.

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